In organ notation, what does the abbreviation 'ab' indicate?

In organ notation, what does the abbreviation 'ab' indicate?

• A. On; engage the organ stops
• B. Off; organ stops or mutes
• C. Mute; dampen the sound
• D. Detach; staccato articulation

Answer: (B)

Abbreviations like this point to registration changes—the stops that are helping shape the sound. When you see this mark, it means turn the given stop off, so that voice or timbre stops sounding. It’s a directive to withdraw a stop (or mute that line) to change the overall color and volume of the organ texture. It’s not about turning a stop on, nor about a general mute or a separate articulation like staccato; it specifically indicates that the stop should be deactivated.

Abbreviations like this point to registration changes—the stops that are helping shape the sound. When you see this mark, it means turn the given stop off, so that voice or timbre stops sounding. It’s a directive to withdraw a stop (or mute that line) to change the overall color and volume of the organ texture. It’s not about turning a stop on, nor about a general mute or a separate articulation like staccato; it specifically indicates that the stop should be deactivated.